Comet exploration mission Rosetta

12/02/2014

Nearly 11 years ago, in March 2004, the space probe Rosetta launched toward its exploration of comet 67P/Churyamov-Gerasimenko. After flying a total of 6.4 billion kilometers to get to the comet, Rosetta has been in orbit around it since August 2014. In November 2014, the Philae lander released from the Rosetta probe, and landed on the comet’s surface.

Rosetta and Philae are already accompanying the comet to its perihelion in August 2015. The probe remains in orbit around the comet while Philae rests on the surface. During this journey, measuring instruments on both modules will exactly observe how this cold and inert chunk of dust and ice awakens as it is heated by the sun.

Scientists are mainly hoping that the data collected will provide information about the comet’s composition. They are convinced that some of the water on Earth comes from impacts by asteroids and comets. It is also probable that numerous organic molecules, such as amino acids—the building blocks of life, came to Earth in this manner.

One single, highly precise antenna on Earth is responsible for all communication with and control of the Rosetta probe and Philae lander during this long voyage. It is located in Western Australia, and stands 40 meters tall. In order to send signals to the modules located more than 500 million kilometers away, and to receive signals from them, the 540-ton antenna must be aligned with the utmost precision.

For certain situations the antenna position may deviate from its nominal value by only 0.006 degrees (21 seconds of arc) The positioning system must ensure this accuracy even under adverse conditions, including winds pressing against the antenna at speeds of up to 60 kilometers per hour. This important positioning task is handled by a servo system in which angle encoders from HEIDENHAIN are responsible for the extremely precise measurement of the position. They have been working without error since the beginning of the mission, and have so played a vital part in the success of all maneuvers to date.